The Reproductive Endocrine Sciences Center of Harvard University represents an interdisciplinary collaboration of research scientists whose investigative efforts focus upon the contemporary issues of reproductive biology. The program establishes and stabilizes an environment of high quality Core Laboratories (Administration, Assay, Cell Culture, Molecular Biology, and Peptide Synthesis/Protein Chemistry); effective leadership by mature, mid-career Core Directors; and a committed cadre of highly interactive Center Investigators. Together, they provide a platform of effective scientific consultations, low cost services, effective technology transfer, and an exciting educational base. As testimony to the quality of its underlying scientific base and effective collegiality of spirit, the Center has experienced considerable growth since its inception 4 years ago. Its initial Il approved Center Investigators and 15 grants located exclusively at the Massachusetts General Hospital has expanded to encompass 18 Investigators (with 5 additional pending approval at submission), 27 NIH-supported grants (with 7 additional pending), 3 affiliated hospitals, and the basic science faculties of Harvard Medical School and Harvard College. This broad platform of interactions has substantially facilitated and expanded the science of individual researchers and their laboratories by establishing a unique sense of community for reproductive investigators university-wide. This matrix has now enabled the emergence as independent investigators of several younger scientists who now constitute the next generation of Center Investigators expanding the vitality of the Center's program and enlarging its scope while maintaining the focus on reproductive biology. The impact of the Center has been remarkable; its growth a testimony to its scientific base; and its leadership effective in maintaining a sense of collegiality and scientific integrity.